Innocent people could be wrongfully jailed under reforms put forward by the child sex abuse royal commission, with the Australian Lawyers Alliance describing the proposal as "dangerous".
The Royal Commission into Institutional Responses to Child Sexual Abuse has released draft bills which would allow more details about an accused person's past, known as tendency and co-incidence evidence, to be put before a jury.
In releasing the draft bills, royal commission chief executive Philip Reed said tendency and co-incidence evidence as well as joint trials, involving a number of alleged victims of the same defendant, could be significant in child sex abuse cases.
"Where the only evidence of child sexual abuse offences is the complainant's evidence, it is likely to be more difficult for the jury to be satisfied beyond reasonable doubt that the offences occurred because the jury is effectively considering the account of one person against the account of another," he said.
"If other complainants or witnesses are able to give evidence that the accused also sexually abused them as a child - considered to be tendency or co-incidence evidence - this may help the jury to be satisfied of the accused's guilt beyond reasonable doubt."
The Australian Lawyers Alliance has accused the royal commission of going too far, saying lowering the threshold of admissible evidence would lead to an increase in wrongful convictions.
"This will mean more evidence gets in and that means the danger of a wrongful convictions," the ALA's spokesman on criminal justice Greg Barns said.
"The jury gets swamped with this material and they think, 'Oh well, he's done it before, he must have done it this time, we'd better convict him'. It will create an increased risk of innocent people going to jail."
A large study of jury behaviour released by the royal commission in May found that evidence of an accused person's "bad character" did not unduly influence a verdict.
Mr Barns said the royal commission is not best placed to make suggestions about fairness in criminal trials.
"(The draft bills) are extraordinary," he said. "I think this royal commission has advocated a particular perspective. After hearing three or four years of horror stories from victims it's understandable they would have that perspective but it doesn't mean they are best placed to be giving advice on fairness in criminal trials. It's very dangerous."
Andrew Morrison SC, the ALA's spokesman on the royal commission, raised concerns that the bills were too broad and would apply nationally to all crimes, not just those involving child sexual abuse.
"The reforms proposed in these draft bills would seriously undermine the right to a fair trial in Australia," he said.
"There are very real risks that such reforms would lead to convictions and prison sentences for innocent people."
Dr Morrison said the ALA supports the commission's work but believes the draft bills overstep the mark.
"In this instance it has gone too far," he said. "Reforming evidence laws is outside of its terms of reference and the proposed bills present a serious risk to the Australian legal system."
A royal commission spokeswoman said legislative reforms to better protect children were in its terms of reference.
The draft has been released for public consultation with the commission welcoming feedback.